1. Field of the Invention
The present invention relates to a liquid discharge head for effecting recording by forming a flying liquid droplet by discharging liquid and a method for manufacturing such a head, and a method for working a substrate, and more particularly, it relates to a method for forming a liquid supply port for receiving liquid within a liquid discharge head as a through-hole passing through an Si (silicon) substrate constituting the liquid discharge head by means of anisotropic etching for silicon.
2. Related Background Art
A liquid discharge recording apparatus (ink jet recording apparatus) for effecting recording by discharging liquid (ink) and by adhering the liquid to a recording medium has been used in various office equipments such as a printer, a copier, a facsimile and the like. The ink jet recording apparatus generally includes a liquid discharge head (ink jet recording head) and an ink supplying system for supplying the ink to the liquid discharge head. The ink jet recording head generally includes discharge energy generating elements for generating energy for discharging the ink, ink discharge ports through which the ink is discharged, ink flow paths communicated with the respective ink discharge ports, and an ink supply port for receiving ink supplied from an ink supply system.
As one of such ink discharge heads, there is a head of so-called side shooter type in which ink droplets are discharged in a direction perpendicular to a plane of a substrate on which ink discharge energy generating elements are formed. In the ink jet recording head of side shooter type, the ink supply port is generally formed as a through-hole passing through the substrate.
As methods for forming the ink supply port as the through-hole in the substrate, a method for forming the port by mechanical working such as sand blast or ultrasonic grinding and a method for forming the port by chemically etching a substrate are well-known (for example, refer to Japanese Patent Application Laid-open No. 62-264957 and U.S. Pat. No. 4,789,425). In particular, a method for forming the through-hole by anisotropic etching for an Si (silicon) substrate is excellent since the through-hole can be formed with high accuracy. The fact that the ink supply port can be formed with high accuracy leads to the fact that a distance from the ink supply port to the ink discharge energy generating element can be shortened, with the result that ink discharge frequency can be increased remarkably (refer to U.S. Pat. No. 4,789,425 and EP 0609911A2).
In the formation of the through-hole by means of the anisotropic etching, if crystal defects locally exist in the Si substrate, in areas where the crystal defects exist, an etching speed is more increased in comparison with areas where the crystal defects do not exist. Consequently, etching abnormality occurs, with the result that there may be dispersion in a width of the formed through-hole in the conventional ink jet recording head manufacturing methods.
Further, upon effecting of the anisotropic etching of silicon, there may be minute dispersion in a time for starting the etching in dependence upon a condition of an etching start surface and etching conditions (density and temperature of etching liquid and the like). Thus, the etching time is normally set to be longer in order to positively pass the ink supply hole through the substrate (i.e., over etching). In the conventional ink jet recording head manufacturing methods, because there is minute difference in the etching starting time, a side etching amount due to the over etching may be differentiated between parts of the substrate and between substrates, with the result that the width of the through-hole may be deviated minutely from a design value.
As mentioned above, if the width of the through-hole constituting the ink supply port, particularly, the open width of the ink supply port on the surface of the substrate on which the ink discharge energy generating elements are formed is deviated from the design value, the distance between the ink discharge energy generating element and the ink supply port is deviated from a design value, with the result that ink discharging property may be subjected to a bad influence to worsen recording quality of the ink jet recording head. Further, if the open width of the ink supply port on the surface of the substrate is greatly deviated from the design value, a driving circuit for the ink discharge energy generating elements may be subjected to a bad influence. As such, the deviation in open width of the ink supply port on the surface of the substrate is a main factor for reducing through-put of the ink jet recording apparatus.